Advances in the molecular biological understanding of gene organization, polymorphisms and expression of many blood group antigens now make it possible to address long-standing problems in Transfusion Medicine. These problems include rapid and objective identification of blood group antibodies, shortages of antibodies with certain specificities, accurate genotyping, antigen typing of a fetus at risk for hemolytic disease of the newborn and antigen typing polytransfused patients. It is the aim of this project to use molecular biology procedures as a complement to classical serological techniques to improve clinical services in these areas of blood group compatibility. We will first determine the effectiveness of synthetic peptides and recombinant polypeptides, containing sequences identical to polymorphic regions of the blood group molecules, to inhibit alloantibodies in vitro. In instances where this approach is ineffective we will use transfectants expressing blood group antigens to absorb antibodies from serum. We will determine the usefulness of these soluble and cell-bound blood group active peptides for the identification of alloantibodies in complex mixtures produced by polytransfused patients in both manual and automated systems. Blood group active synthetic peptides, recombinant polypeptides, transfectants and cotransfectants will also be used as immunogens in mice for the production of monoclonal antibodies to antigens for which good reagents are not currently available. We will investigate the practicality of performing PCR using allele-specific primers and genomic DNA to establish the presence of allelic variants of defined blood group antigens. We will determine the predicted antigen status (K, c, D) of a fetus using DNA from amniocytes and of massively transfused patients using buccal cells. Further, the ability to antigen type large volumes of blood samples for antigens such as Kpb, Jsb and hr/S would bypass serological problems due to either the absence of high quality reagents or of well preserved blood samples. In addition, these methods would permit us to determine the blood group genotype of forensic specimens not adequate for agglutination or absorption testing.